Relationship between the Cultivar Groups Resistant to Rice Bacterial Blight and Indica-Japonica Classification

Abstract

In order to study the relationship between the diversity of rice cultivar groups carrying different resistant genes to bacterial blight(BB) and Indica-Japonica classification, the Indica (Z≤O) and Japonica (O<Z) types defined by the discriminant Z-function (Sato 1991) were studied for the BB resistant groups in relation to the isozyme types. Based on the combination of phenol reaction(Ph), KCIO₃ resistance(K) and apiculus hair length(H), the 832 cultivars were classified into Indica and Japonica types. Among the total cultivars, it was found that the distribution of Z score in the range from -1.8 to 2.0 formed three peaks:one peak (Z≤O) corresponding to Japonica type, and two peaks (O<Z≤1.4, 1.4<Z) corresponding to Indica type.Cultivars showing Ph-negative and K-susceptible tended to form the peak of O<Z≤1.4, and this peak was not the minority in the BB resistant groups. Therefore, the peaks of O<Z≤1.4 and 1.4<Z were tentatively separated as Interrnediate and Indica types respectively. In the Java 14 group, almost 80% consisted of isozyme type VI, and the type VI was composed of both Japonica and Intermediate types with an even balance. The TKM 6 and Cas 209 groups consisted of isozyme type I, and almost all cultivars were Indica and Intermediate types. The DZ 192 group consisted of type II, and typeII was also classified as Indica and Intermediate types. The TN 1 group involved type I predominantly and a small group of type VI as well. In this group, most cultivars of type VI were Japonica type, while Intermediate type was frequent in the type I. Based on these results, it was found that isozyme type I of the TKM 6, Cas 209 and TN 1 groups as well as isozyme type II of the DZ 192 group were composed of Intermediate and Indica types. It was also shown that Japonica type was related to the type VI of the Java 14 and TN 1 groups.